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Date:   Tue, 3 Apr 2018 17:02:46 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Matthew Garrett <mjg59@...gle.com>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        David Howells <dhowells@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        James Morris <jmorris@...ei.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Justin Forbes <jforbes@...hat.com>,
        linux-man <linux-man@...r.kernel.org>, joeyli <jlee@...e.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot

On Tue, Apr 3, 2018 at 4:47 PM, Matthew Garrett <mjg59@...gle.com> wrote:
>> Another way of looking at this: if lockdown is a good idea to enable
>> when you booted using secure boot, then why isn't it a good idea when
>> you *didn't* boot using secure boot?
>
> Because it's then trivial to circumvent and the restrictions aren't worth
> the benefit.

Bullshit.

If there those restrictions cause problems, they need to be fixed regardless.

In fact, from a debuggability standpoint, you want to find the
problems early, on those kernel development machines that had secure
boot explicitly turned off because it's such a pain.

And if they can't be fixed, then the user is going to disable lockdown
regardless of how he booted the machine.

In no situation is "depending on how you booted" a good choice.

Either you can enable it or you can't. If you can, good. And if you
can't, it has nothing to do with secure boot.

            Linus

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